[llvm] 7454439 - [zero-call-used-regs] Mark only non-debug instruction's register as used
Shivam Gupta via llvm-commits
llvm-commits at lists.llvm.org
Tue Jan 24 21:33:44 PST 2023
Author: Shivam Gupta
Date: 2023-01-25T11:04:22+05:30
New Revision: 7454439674a4a78b9fc9dc9ffba7a60717ee310b
URL: https://github.com/llvm/llvm-project/commit/7454439674a4a78b9fc9dc9ffba7a60717ee310b
DIFF: https://github.com/llvm/llvm-project/commit/7454439674a4a78b9fc9dc9ffba7a60717ee310b.diff
LOG: [zero-call-used-regs] Mark only non-debug instruction's register as used
zero-call-used-regs pass generate an xor instruction to help mitigate
return-oriented programming exploits via zeroing out used registers. But
in this below test case with -g option there is dbg.value instruction
associating the register with the debug-info description of the formal
parameter d, which makes the register appear used, therefore it zero the
register edi in -g case and makes binary different from without -g option.
The pass should be looking only at the non-debug uses.
$ cat test.c
char a[];
int b;
__attribute__((zero_call_used_regs("used"))) char c(int d) {
*a = ({
int e = d;
b;
});
}
This fixes https://github.com/llvm/llvm-project/issues/57962.
Differential Revision: https://reviews.llvm.org/D138757
Added:
llvm/test/CodeGen/X86/zero-call-used-regs-debug-info.mir
Modified:
llvm/lib/CodeGen/PrologEpilogInserter.cpp
Removed:
################################################################################
diff --git a/llvm/lib/CodeGen/PrologEpilogInserter.cpp b/llvm/lib/CodeGen/PrologEpilogInserter.cpp
index 88bd3ec1b823e..cc70ec4776506 100644
--- a/llvm/lib/CodeGen/PrologEpilogInserter.cpp
+++ b/llvm/lib/CodeGen/PrologEpilogInserter.cpp
@@ -1230,7 +1230,11 @@ void PEI::insertZeroCallUsedRegs(MachineFunction &MF) {
BitVector UsedRegs(TRI.getNumRegs());
if (OnlyUsed)
for (const MachineBasicBlock &MBB : MF)
- for (const MachineInstr &MI : MBB)
+ for (const MachineInstr &MI : MBB) {
+ // skip debug instructions
+ if (MI.isDebugInstr())
+ continue;
+
for (const MachineOperand &MO : MI.operands()) {
if (!MO.isReg())
continue;
@@ -1240,6 +1244,7 @@ void PEI::insertZeroCallUsedRegs(MachineFunction &MF) {
(MO.isDef() || MO.isUse()))
UsedRegs.set(Reg);
}
+ }
// Get a list of registers that are used.
BitVector LiveIns(TRI.getNumRegs());
diff --git a/llvm/test/CodeGen/X86/zero-call-used-regs-debug-info.mir b/llvm/test/CodeGen/X86/zero-call-used-regs-debug-info.mir
new file mode 100644
index 0000000000000..68505b6d94528
--- /dev/null
+++ b/llvm/test/CodeGen/X86/zero-call-used-regs-debug-info.mir
@@ -0,0 +1,142 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -run-pass=prologepilog -o - %s | FileCheck %s
+
+# Test that the presence of debug instructions doesn't trigger arbitrary registers that are unused to be zeroed out.
+
+--- |
+ ; ModuleID = 'zero-call-used-regs-debug-info.ll'
+ source_filename = "zero-call-used-regs-debug-info.c"
+ target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+ target triple = "x86_64-unknown-linux-gnu"
+
+ @b = dso_local local_unnamed_addr global i32 0, align 4, !dbg !0
+ @a = dso_local local_unnamed_addr global [1 x i8] zeroinitializer, align 1, !dbg !5
+
+ ; Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(readwrite, argmem: none, inaccessiblemem: none) uwtable
+ define dso_local signext i8 @c(i32 noundef %d) local_unnamed_addr #0 !dbg !19 {
+ entry:
+ call void @llvm.dbg.value(metadata i32 %d, metadata !23, metadata !DIExpression()), !dbg !26
+ call void @llvm.dbg.value(metadata i32 %d, metadata !24, metadata !DIExpression()), !dbg !27
+ %0 = load i32, ptr @b, align 4, !dbg !28, !tbaa !29
+ %conv = trunc i32 %0 to i8, !dbg !33
+ store i8 %conv, ptr @a, align 1, !dbg !34, !tbaa !35
+ ret i8 undef, !dbg !36
+ }
+
+ ; Function Attrs: nocallback nofree nosync nounwind speculatable willreturn memory(none)
+ declare void @llvm.dbg.value(metadata, metadata, metadata) #2
+
+ attributes #0 = { mustprogress nofree norecurse nosync nounwind willreturn memory(readwrite, argmem: none, inaccessiblemem: none) uwtable "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" "zero-call-used-regs"="used" }
+ attributes #1 = { mustprogress nofree norecurse nosync nounwind willreturn memory(none) uwtable "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
+ attributes #2 = { nocallback nofree nosync nounwind speculatable willreturn memory(none) }
+
+ !llvm.dbg.cu = !{!2}
+ !llvm.module.flags = !{!12, !13, !14, !15, !16, !17}
+ !llvm.ident = !{!18}
+
+ !0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+ !1 = distinct !DIGlobalVariable(name: "b", scope: !2, file: !3, line: 2, type: !11, isLocal: false, isDefinition: true)
+ !2 = distinct !DICompileUnit(language: DW_LANG_C11, file: !3, producer: "clang version 16.0.0 (https://github.com/llvm/llvm-project.git ba5acedd979aa94a81be555e0add8e4421499d4f)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, globals: !4, splitDebugInlining: false, nameTableKind: None)
+ !3 = !DIFile(filename: "zero-call-used-regs-debug-info.c", directory: "/home/xgupta/compiler/llvm-project/build/bin", checksumkind: CSK_MD5, checksum: "fe3a5f45289411a008e07c7debb490ca")
+ !4 = !{!5, !0}
+ !5 = !DIGlobalVariableExpression(var: !6, expr: !DIExpression())
+ !6 = distinct !DIGlobalVariable(name: "a", scope: !2, file: !3, line: 1, type: !7, isLocal: false, isDefinition: true)
+ !7 = !DICompositeType(tag: DW_TAG_array_type, baseType: !8, size: 8, elements: !9)
+ !8 = !DIBasicType(name: "char", size: 8, encoding: DW_ATE_signed_char)
+ !9 = !{!10}
+ !10 = !DISubrange(count: 1)
+ !11 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+ !12 = !{i32 7, !"Dwarf Version", i32 5}
+ !13 = !{i32 2, !"Debug Info Version", i32 3}
+ !14 = !{i32 1, !"wchar_size", i32 4}
+ !15 = !{i32 8, !"PIC Level", i32 2}
+ !16 = !{i32 7, !"PIE Level", i32 2}
+ !17 = !{i32 7, !"uwtable", i32 2}
+ !18 = !{!"clang version 16.0.0 (https://github.com/llvm/llvm-project.git ba5acedd979aa94a81be555e0add8e4421499d4f)"}
+ !19 = distinct !DISubprogram(name: "c", scope: !3, file: !3, line: 3, type: !20, scopeLine: 3, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !22)
+ !20 = !DISubroutineType(types: !21)
+ !21 = !{!8, !11}
+ !22 = !{!23, !24}
+ !23 = !DILocalVariable(name: "d", arg: 1, scope: !19, file: !3, line: 3, type: !11)
+ !24 = !DILocalVariable(name: "e", scope: !25, file: !3, line: 5, type: !11)
+ !25 = distinct !DILexicalBlock(scope: !19, file: !3, line: 4, column: 9)
+ !26 = !DILocation(line: 0, scope: !19)
+ !27 = !DILocation(line: 0, scope: !25)
+ !28 = !DILocation(line: 6, column: 5, scope: !25)
+ !29 = !{!30, !30, i64 0}
+ !30 = !{!"int", !31, i64 0}
+ !31 = !{!"omnipotent char", !32, i64 0}
+ !32 = !{!"Simple C/C++ TBAA"}
+ !33 = !DILocation(line: 4, column: 8, scope: !19)
+ !34 = !DILocation(line: 4, column: 6, scope: !19)
+ !35 = !{!31, !31, i64 0}
+ !36 = !DILocation(line: 8, column: 1, scope: !19)
+ !37 = distinct !DISubprogram(name: "main", scope: !3, file: !3, line: 9, type: !38, scopeLine: 9, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !40)
+ !38 = !DISubroutineType(types: !39)
+ !39 = !{null}
+ !40 = !{}
+ !41 = !DILocation(line: 9, column: 14, scope: !37)
+
+...
+---
+name: c
+alignment: 16
+exposesReturnsTwice: false
+legalized: false
+regBankSelected: false
+selected: false
+failedISel: false
+tracksRegLiveness: true
+hasWinCFI: false
+callsEHReturn: false
+callsUnwindInit: false
+hasEHCatchret: false
+hasEHScopes: false
+hasEHFunclets: false
+debugInstrRef: true
+failsVerification: false
+tracksDebugUserValues: true
+registers: []
+liveins: []
+frameInfo:
+ isFrameAddressTaken: false
+ isReturnAddressTaken: false
+ hasStackMap: false
+ hasPatchPoint: false
+ stackSize: 0
+ offsetAdjustment: 0
+ maxAlignment: 1
+ adjustsStack: false
+ hasCalls: false
+ stackProtector: ''
+ functionContext: ''
+ maxCallFrameSize: 4294967295
+ cvBytesOfCalleeSavedRegisters: 0
+ hasOpaqueSPAdjustment: false
+ hasVAStart: false
+ hasMustTailInVarArgFunc: false
+ hasTailCall: false
+ localFrameSize: 0
+ savePoint: ''
+ restorePoint: ''
+fixedStack: []
+stack: []
+callSites: []
+debugValueSubstitutions: []
+constants: []
+machineFunctionInfo: {}
+body: |
+ bb.0.entry:
+ ; CHECK-LABEL: name: c
+ ; CHECK: DBG_VALUE $edi, $noreg, !23, !DIExpression(), debug-location !26
+ ; CHECK-NEXT: DBG_VALUE $edi, $noreg, !24, !DIExpression(), debug-location !27
+ ; CHECK-NEXT: renamable $al = MOV8rm $rip, 1, $noreg, @b, $noreg, debug-location !28 :: (dereferenceable load (s8) from @b, align 4, !tbaa !29)
+ ; CHECK-NEXT: MOV8mr $rip, 1, $noreg, @a, $noreg, killed renamable $al, debug-location !34 :: (store (s8) into @a, !tbaa !35)
+ ; CHECK-NEXT: RET 0, undef $al, debug-location !36
+ DBG_VALUE $edi, $noreg, !23, !DIExpression(), debug-location !26
+ DBG_VALUE $edi, $noreg, !24, !DIExpression(), debug-location !27
+ renamable $al = MOV8rm $rip, 1, $noreg, @b, $noreg, debug-location !28 :: (dereferenceable load (s8) from @b, align 4, !tbaa !29)
+ MOV8mr $rip, 1, $noreg, @a, $noreg, killed renamable $al, debug-location !34 :: (store (s8) into @a, !tbaa !35)
+ RET 0, undef $al, debug-location !36
+
+...
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